Technique for optimizing cut-through for broadcast and multi-cast packets in a multi-port bridge for a local area network

• US 6,738,384 B1
• Filed: 03/19/1999
• Issued: 05/18/2004
• Est. Priority Date: 09/17/1997
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Inventors: Chung, David
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): George, Keith M.
• Application Number:
  US09/272,833
• Time in Patent Office: 1,887 Days
• Field of Search: 370/401, 370/402, 370/403, 370/404, 370/405, 370/406, 370/412, 370/413, 370/414, 370/415, 370/416, 370/417, 370/418, 370/428, 370/429
• US Class Current: 370/412
• CPC Class Codes: H04L 12/18 for broadcast or conference , e.g. multicast
• CPC Class Codes: H04L 12/40013 Details regarding a bus controller
• CPC Class Codes: H04L 12/413 with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
• CPC Class Codes: H04L 12/42 Loop networks
• CPC Class Codes: H04L 12/462 LAN interconnection over a bridge based backbone
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/135 by jamming the transmission media
• CPC Class Codes: H04L 47/30 in combination with information about buffer occupancy at either end or at transit nodes
• CPC Class Codes: H04L 49/102 using shared medium, e.g. bus or ring
• CPC Class Codes: H04L 49/201 Multicast operation; Broadcast operation
• CPC Class Codes: H04L 49/351 for local area network [LAN], e.g. Ethernet switches
• CPC Class Codes: H04L 49/354 for supporting virtual local area networks [VLAN]
• CPC Class Codes: H04L 49/90 Buffering arrangements
• CPC Class Codes: H04L 49/901 using storage descriptor, e.g. read or write pointers
• CPC Class Codes: H04L 49/9057 Arrangements for supporting packet reassembly or resequencing
• CPC Class Codes: H04L 49/9073 Early interruption upon arrival of a fraction of a packet
• CPC Class Codes: H04L 49/9089 replacing packets in a storage arrangement, e.g. pushout

Abstract

A technique for optimizing cut-through for broadcast and multi-cast data packets in a multi-port bridge for a local area network (LAN). The multi-port bridge includes a plurality of ports for communicating packets with an associated segment of the LAN. Each of the ports is coupled to a data bus for communicating packets among the ports. A packet buffer is coupled to the data bus for temporarily storing packets undergoing communication between the ports. At least one of the ports includes a transmit packet store for receiving packets to be transmitted by the port and a broadcast packet store for receiving broadcast and multi-cast packets to be transmitted by the port wherein the broadcast packet store receives a broadcast or multi-cast packet only when the transmit packet store is occupied. The transmit packet store can receive a packet from the packet buffer or at the same time the packet buffer receives the packet. Because the broadcast packet store receives the broadcast or multi-cast packet from the data bus at the same time the packet buffer receives it, even when the transmit packet store is occupied, the invention minimizes the number of ports which need to retrieve such a broadcast or multi-cast packet from the packet buffers. This minimizes bandwidth of the data bus occupied by retrieving broadcast and multi-cast data packets from the packet buffers.

Claims

1. A multi-port bridge for a local area network (LAN), the multi-port bridge comprising:

a. a plurality of ports to communicate packets with an associated segment of the LAN;

b. a data bus coupled to each of the plurality of ports to communicate packets among the ports; and

c. a packet buffer coupled to the data bus to temporarily store packets undergoing communication between the ports;

wherein at least one of the plurality of ports includes a transmit packet store to receive packets to be transmitted by the port to the segment of the LAN associated with the port and a broadcast packet store to receive broadcast packets to be transmitted by the port to the segment of the LAN associated with the port wherein the broadcast packet store receives a broadcast packet only when the transmit packet store is occupied.

2. The multi-port bridge according to claim 1 wherein the broadcast packet store receives the broadcast packet at the same time the packet buffer receives the broadcast packet.

3. The multi-port bridge according to claim 2 wherein the transmit packet store receives a packet to be transmitted by the port from the packet buffer.

4. The multi-port bridge according to claim 2 wherein the transmit packet store receives a packet to be transmitted at the same time the packet buffer receives the packet.